1. Field of the Invention
This invention relates, in general, to a shock and vibration absorbing seat support for a vehicle and, in particular, to a combination beam seat support including a shock and vibration damping layer positioned between relatively movable structural members to absorb vibration and shock loads. As disclosed, the invention has particular application to bicycles, but is not limited thereto.
2. Description of the Prior Art
The problem of eliminating vibration and shocks to smooth the ride for a person sitting upon a vehicle traveling over rough ground has been a serious one since the development of the first vehicle. Solutions have typically involved separating the wheels of the vehicle from the vehicle frame by means of springs and shock absorbers as well as spring mounting the vehicle seat on the vehicle frame. In automobiles and tractors, for example, seats have been mounted using both coil springs, leaf springs and combinations thereof.
Referring particularly to the bicycle art wherein the present invention has relevant application, the seat support almost universally takes the form of a rigid tubular member inserted in a cooperating near vertical tube portion of a rigid bicycle frame. A seat, which may include a form of resilient spring cushioning, is typically mounted to the top of the tubular seat support.
The inflated tires mounted on the wheels are the initial and sometimes the only means for shock absorption on a bicycle. Low-pressure balloon tires of the type typically used for so-called "mountain" bikes can provide some limited shock and vibration absorption, but these bikes are often used in terrain where such severe shocks and vibrations are encountered that the ride smoothing effect of the tires is insufficient. Further, in other types of bikes where tire size is small and air pressure within the tire high, the ability of the tire to absorb shocks and vibration is near nonexistent. Consequently, most road shocks and vibrations experienced by present bicycles are transmitted directly to the bicycle seat and, thence, to the rider. In extreme cases, such as during long-distance races or during mountain bike races, the abuse suffered by riders from continual shocks and vibrations has been known to lead to temporary nerve damage, muscle cramps, and severe rider discomfort. See Bicycle Guide, August 1988, pages 75-78. Even during more normal riding conditions, shocks and vibrations create fatigue, decrease rider comfort and cause pain, particularly in that portion of the anatomy in contact with the bicycle seat.
In addition, the use of metal frames for bicycles has principally been driven by the requirement that the frame be able to withstand vibration and the substantial rider weight loads that are often unresiliently placed on the bicycle frame as a result of the bicycle hitting a severe bump. It is for this reason that lightweight bicycle frames, such as those formed of resin-bounded fibers surrounding rigid foam cores, have not found widespread acceptance.
Many attempts have been made to improve the spring mounting of bicycle seats, including the use of leaf springs as shown, for example, in U.S. Pat. Nos. 1,469,136; 2,244,709; and 2,497,121. Such constructions have the drawback of allowing the rider to be alternately depressed downwardly and catapulted upwardly in a magnified and relatively uncontrolled fashion. In addition, such seats tend to sway laterally when the bicycle turns or rotates torsionally in an unstable and uncomfortable manner. A combination leaf spring and parallel motion bar seat support is shown in U.S. Pat. No. 1,416,942. A tricycle having a coil spring seat support allowing substantial vertical seat movement is shown in U.S. Pat. No. 4,162,797.
The problem of reducing vibration and shock to a rider has also been attempted to be solved through the use of shock absorbers and springs between the bicycle frame and wheels rather than between the seat and the frame. Examples of such arrangements developed over the past ninety years are shown in U.S. Pat. Nos. 423,471; 457,080; 468,823; 505,753; 518,338; 953,697; 2,160,034; 2,283,671; 2,446,731; 2,485,484; 2,976,056; 3,459,441; and, 4,421,337. These patents show the seriousness of the problem solved by the present invention and the numerous attempts to alleviate shocks and vibrations delivered to bicycle riders which have been made in the past. In spite of these attempts, almost all bicycle seats in use today have little ability to absorb vibration or shock. Substantial need still exists in the bicycle art, as well as in the vehicle seat support art in general, for an improved shock and vibration absorbing seat support.